Threading of Long End-Functionalized Organic Molecules into Cyclodextrins: Structural Analysis in Aqueous Solution by NMR Spectroscopy and in the Solid State by X-Ray Crystallography

Author(s): K. Yannakopoulou, I. M. Mavridis.

Journal Name: Current Organic Chemistry

Volume 8 , Issue 1 , 2004

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The length of guest molecules determines the stoichiometry of inclusion complexes of long endfunctionalized molecules with cyclodextrins in aqueous solution. Molecules up to 10-12 Å form primarily 1:1 host:guest adducts, even if they have to curve inside the cavity, whereas longer molecules form mixtures of 1:1 and 2:1 adducts in equilibrium with each other. The width of the cyclodextrin cavity determines the host-guest recognition, therefore aliphatic chains have a preference for α-cyclodextrin, whereas aromatic rings fit better to β-cyclodextrin. If the size of the cyclodextrin cavity is large relative to the thickness of the guest, and the guest has a propensity to dimerise, then 2:2 host:guest adducts, may be observed. Out of the various mixtures in the aqueous solutions, crystallization of single-stoichiometry inclusion complexes takes place and the guests end-groups play a key role in the crystal packing. It seems, therefore, that the length of the guest influences critically the first-order organization of cyclodextrins in the aqueous solution, whereas the end-functional groups influence heavily the further organization of the initial assemblies into larger supramolecular arrays, as expressed by the packing modes in the crystal.

Keywords: Cyclodextrins, supramolecular, single-stoichiometry

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Article Details

Year: 2004
Page: [25 - 34]
Pages: 10
DOI: 10.2174/1385272043486106

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